1. Field of Invention
This invention relates to the preparation of acetic acid from methyl formate. More particularly, the invention is concerned with a rhodium catalyzed, halogen promoted rearrangement of methyl formate into acetic acid.
2. Prior Art
The direct conversion of methyl formate into acetic acid is already known. U.S. Pat. No. 2,508,513 claims a liquid-phase process for making acetic acid by heating methyl formate in the presence of a carbonyl-forming metal catalyst and a halogen. The catalysts are further defined as one or more of the iron metals, preferably nickel. Other metals of less activity are tungsten, vanadium, antimony, and bismuth. The process of this patent is a high temperature, above 300.degree. C., process. Carbon monoxide is advantageous to the process. No yields are reported; but the reaction product contains acetic acid, methyl acetate, and some formic acid.
Another patent, U.S. Pat. No. 1,697,109, claims the vapor-phase isomerization of methyl formate into acetic acid by heating it in the presence of a catalyst. The catalysts are either (1) metal acetates which decompose with the formation of acetic acid at a temperature under 450.degree. C. or (2) a metal compound capable of forming said acetates. Typical catalysts are salts of copper, tin, lead, zinc, and aluminum. The reaction is carried out at temperatures in the range of 100.degree.-450.degree. C., preferably 200.degree.-300.degree. C. No examples are given.